田光 / Tian Guang
田光 / Tian Guang enters the wiki through 《资治通鉴·秦纪》114-2｜燕国刺杀秦始皇为何会选荆轲 as the elder wise man 居武 recommends to 燕太子丹 after Taizi Dan rejects a slow coalition strategy against 秦国. In the private meeting, Tian Guang understands that Dan’s language of Yan and Qin being unable to coexist points toward assassination.
Tian Guang refuses to present himself as the operative answer. He uses the old-horse image to distinguish his past reputation from his current capacity, then recommends his friend 荆轲 as the more suitable person. The source makes that recommendation morally heavy because Tian Guang has not first asked Jing Ke whether he wants the mission.
His suicide is the episode’s hinge. Tian Guang says Taizi Dan’s secrecy warning implies distrust and that he therefore does not deserve the name of a high-minded侠士. The source reads the death less as despair than as a three-part act: sealing the secret, guaranteeing the plan, and pressing Jing Ke to live up to the义士 role Tian Guang has just assigned him.